Method of distilling hydrocarbon oils



NOV. 8, 1938. R c POWELL METHOD OF DISTILLING HYDROCARBON OILS Original Filed July 12, 1932 ['IIf fffillfllv Patented Nov. 8, 1938 2,136,172 METHOD OF msrrgggo HYDROCARBON Ross C. Powell,

The Texas Company, poration of Delaware Application July Forest Hills, N. Y., assignor to New York, N. Y., a cor- Renewed December 2, 1933 4 Claims.

This invention relates to the distillation of hydrocarbon oils, and in particular to a method of distilling a suitable petroleum oil under vacuum to produce a maximum yield of lubricating oil dis- ;3 tillates.

The invention contemplates a method of distilling a lubricating oil stock, such as a reduced crude from which, preferably, all fractions lighter than lubricating components have been distilled, wherein the lubricating oil stock is heated to a moderate temperature and a more refractory oil, such as a kerosene distillate or a gas oil, is heated to a temperature well above that to which the lubricating oil stock is heated and the oils are directly admixed and delivered into a zone of subatmospheric pressure conditions where all components except the heavy asphaltic or tarry materials are distilled.

In the distillation of a lubricating oil stock, as ordinarily practiced in the art, the oil may be heated, usually in a coil in one step, to a vaporizing temperature and then be distilled under vacuum, with or without steam, to yield a desired lubricating oil distillate. The yield of distillate depends upon the temperature and pressure conditions maintained in the distillation zone. It is exceedingly difficult however to maintain the stock at high enough temperature, even under high vacuum, to effect distillation of the more valuable high viscosity fractions of the oil as they tend to decompose and lose their viscosity at about the temperatures of their boiling points. Even under the most favorable conditions of heating, where the amount of time during which the oil is under the highest temperature is reduced to a minimum, it is still diflicult to heat the oil sufficiently to effect vaporization of the highest boiling fractions, because temperature of the tubes or vessel in which it is heated tends to effect decomposition of that oil directly in contact with the heating surfaces.

It is accordingly an object of the invention to provide a method whereby a lubricating oil stock may be heated to a temperature adequate to effect the distillation of substantially all of the lubricating fractions without appreciable decomposition and only the tarry or asphaltic constituents remain as a residue.

The invention will be better understood in connection with the accompanying drawing which is a diagrammatic view in elevation showing a preferred embodiment of apparatus suitable for carrying out the process of the invention.

Referring to the drawing: A pump I having a 55 suction line 2 and a discharge line 3 is arranged the required high skin to deliver oil from 12, 1932, Serial No. 622,042

a source (not shown) to preheating coil 4 situated in the upper portion of a distillation chamber 5. The arrangement is such that an oil may be partially heated in said coil by interchange with hot vapors chamber.

developed in said A line 6 connects the heater coil 4 at its outlet with a heater coil 1 in an oil,

situated in a furnace 8 wherewhich has been partially heated in the coil 4, may be heated to a higher temperature. A pump ll having a suction line I2 and a discharge line I3 is adapted to take suction on a body of oil in a reservoir I4 and deliver said oil to a heater coil l5 of the furnace 8.

A transfer line 2 heated oil from the heater coil 1 5 and a transfer line a more highly heate to a convergence with the situated in the hottest part 0 is arranged to deliver a to the chamber 2! is arranged to deliver oil from the heater coil l5 line 2| near the tower 5 where the two oils are commingled and delivered into the chamber The upper portion of the chamber 5 may be equipped with suitable bubble or trap trays BI, 32, 33, 34, and 36 for collecting condensate,

while the lower portion may 38, 39 and 40. Draw-off lines suitable baflies 31,

be equipped with 4|, 42 and 43 are provided for trapping out and withdrawing desired of said trays, a cool condensate from one or more er 44 being provided to further cool the streams of oil moving through the lines 4|, 42 and 43.

Steam may be admitted to the chamber 5 through a line 52 to aid in the vaporization and a pump 5| is provided for taking suction through the line to withdraw an unvaporized portion of the oil from the lower portion of the chamber 5.

An overhead line vapor fraction from 55 is adapted to deliver a the chamber 5 to a surface or coil condenser 56, for condensing all of the overhead vapor except the water and lighter hydrocarbon vapors.

Cooling water to effect the condensation may be supplied by a line 51 (from a source not shown). returning condensate line 59 is provided A line 58 is provided for to the reservoir I4, and a therefrom for drawing off any slight amount of water which may become entrained and collected in the reservoir. A jet condenser fill having a water or steam inlet Bi and an outlet 62 is provided for condensing the remaining vapor and cooling any uncondensable gas that might have been formed. While a jet condenser is mentioned, it is to be understood that a barometric stead, or may be use condenser may be used ind in addition to the jet condenser, followed by one or more stages of jet condensation, so as to reduce the pressure in the chamber 5 substantially below atmospheric.

In a preferred method of operation a lubricating oil stock, for example a reduced crude, may be partially heated by passing it through the heater coil 4 in heat exchange relation with hot vapors developed in the chamber 5. The partially heated oil may be heated in the heater coil 1 to a moderately high temperature, which may be of the order of 650 F., being somewhat lower than the temperature at which decomposition occurs but high enough to effect vaporization of certain of the lubricating fractions. A more refractory oil, for example a kerosene distillate or a gas oil, may be separately heated in the heater coil I5 to a higher temperature, which may be of the order of 950 F.

The highly heated oil from the heater coil l5 may be commingled with the less highly heated oil from the heater coil 1 and the mixture be immediately delivered into chamber 5. The temperatures and proportions of lubricating stock and refractory oil heated may be regulated so as to obtain any temperature of the mixture that may be desirable. For example, a lubricating oil stock may be heated to a temperature of say 650 F. and have admixed therewith a predetermined amount of a more refractory oil which has been heated to a temperature of say 950 F. whereby a temperature for the mixture of the order of 810 F. may be established.

A lubricating oil stock if retained for an appreciable length of time at this elevated temperature will tend to decompose and to lose its viscosity. It is important therefore that the period of time the oil remains at the elevated temperature be as short as practicable. Accordingly, the heated oil may be delivered immediately to the chamber 5 in which a subatmospheric pressure is preferably maintained and steam may be admitted through the line 52 to assist in the distillation wherein a greater portion of the sensible heat is quickly released by vaporization.

A greater portion of the lubricating oil stock, together with the more refractory oil, will be vaporized in said chamber. The hot vapors moving upward through the expansion chamber may be subjected to cooling and condensation in the upper portion of the chamber by indirect heat interchange with the cold charge oil moved through the heater coil 4 and by contact with refluxing liquid collecting in pools on the several trays, 3|, 32, 33, 34, 35 and 36. Desired distillate fractions may be withdrawn from the trays at appropriate elevations in the upper portion of the chamber 5 and discharged through the draw-off lines M, 42 and 43.

Substantially all of the lower boiling more refractory oil used as a heat transfer medium will pass overhead from the chamber 5. This vapor is subjected to condensation in the condenser 56 and is returned to the reservoir M to be recycled through the coil [5 and the remainder of the system, as previously described.

It will not be desirable, however, to condense in the condenser 56 the lower boiling products, such as gasoline distillate, which might have been unintentionally produced by decomposition in the operation, nor the steam introduced to aid the vaporization. These substances are preferably condensed in the jet condenser 60 and together with the uncondensable gases, which are developed in the operation, are discharged from the system.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A method of separating lubricating oils from topped crude oil which comprises heating the oil to a temperature below cracking, heating a light refractory oil of the character of kerosene to a cracking temperature, rapidly mixing the two heated oils and immediately passing the mixture into a fractionating column in which the mixed oils are substantially flashed into vapors, fractionating the vapors therein, while maintaining a substantial vacuum, into overhead vapors comprising the light refractory oil, intermediate fractions comprising light, medium and heavy lubricating oils and a heavy tarry residue.

2. The method of separating lubricating oils from a lubricating oil stock which comprises heating the lubricating oil stock to a temperature below cracking, separately heating a lighter refractory oil of the character of a gas oil to a cracking temperature, rapidly mixing the two heated oils, immediately introducing the mixture into a fractionating column maintained under a substantial vacuum and in which the mixed oils are substantially flashed into vapors, fractionating the vapors therein into overhead vapors comprising the light refractory oil, intermediate fractions comprising light, medium and heavy lubricating oils and a heavy tarry residue.

from a lubricating oil stock which comprises heating the lubricating oil stock to a temperature below cracking, separately heating a lighter refractory oil of the character of a gas oil to a cracking temperature, rapidly mixing the two heated oils, immediately introducing the mixture into a fractionating column maintained under a substantial vacuum and in which the mixed oils are substantially flashed into vapors, fractionating the vapors therein into overhead vapors comprising the light refractory oil, intermediate fractions comprising light, medium and heavy lubricating oils and a heavy tarry residue, condensing the overhead and returning the condensed light refractory oil to the heating step in a cyclic manner.

4. The method of separating lubricating oils from a lubricating heating the lubricating oil stock to a temperature below cracking, separately heating a lighter refractory oil of the character of a gas oil to a cracking temperature, rapidly mixing the two heated oils, immediately introducing the mixture into a fractionating column maintained under a substantial vacuum and in which the mixed oils are substantially flashed into vapors, introducing steam into the column, fractionating. the vapors therein into overhead vapors comprising the light refractory oil and steam, intermediate fractions comprising light, medium and heavy lubricating oils and a heavy tarry residue, condensing the overhead light refractory oil vapors and returning the condensed light refractory oil to the heating step in a cyclic manner while discharging the steam from the system.

ROSS C. POWELL.

light refractory oil vapors oil stock which comprises 

